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Dental problems are often blamed for poor condition and weight loss in horses. They are widely thought to interfere with chewing and grinding of food, which is swallowed before being chewed adequately. This may limit the nutrients that can be released from the food. Routine floating of teeth is said to allow the horse to chew properly and so maintain or improve condition.

But does it really help? Recent research questions the value of routine dental treatment in healthy horses. The study, carried out at the Western College of Veterinary Medicine, University of Saskatchewan assessed the effect of floating (rasping) on weight gain and body condition, in horses fed various diets. It also looked at whether floating the teeth improved the digestibility of the food.
Floating: no effect on weight gain
Fifty-six pregnant mares that had not had dental treatment previously were used for the study. They were divided into four groups and each group was fed a different diet. One group was fed hay only. The others received oats, soy pellets or canola meal pellets in addition to the hay.

Lead researcher Dr James Carmalt carried out a full dental examination on each horse. He recorded all dental defects that were present. The most common abnormality was sharp enamel points at the edge of the cheek teeth, present in about 80% of horses. Three quarters of the horses that had sharp points also had soft tissue ulcers on the cheeks or tongue. About 70% of the horses had stepped teeth - (teeth that stand higher than their neighbors)- always on the lower jaw.

Once the initial examination was complete, half of the horses in each feed group were chosen at random to be treated. Treatment included removing sharp enamel points, restoring the rostro-caudal (front to back) movement of the jaw, grinding down step teeth, correcting wave mouth, and removing hooks. To ensure consistency, Dr Carmalt performed all the treatments himself. He was not told which feed each horse was receiving to avoid bias.

The research team monitored body weight and condition score. They also assessed the digestibility of the food and measured the average size of particles in the feces to assess how efficiently the horses were chewing their food.

They found that routine dental care did not produce weight gain or improve body condition. It was interesting that "quidding", dropping half-chewed food from the mouth, was not more common in horses with dental defects and did not decline after treatment.

The presence of any particular abnormality - such as ulcers or sharp enamel points, did not appear to affect the digestibility of the food. Similarly, routine dental care did not significantly improve digestibility.

However, diet had a significant effect on weight gain. Horses that received oats or pellets in addition to the hay put on significantly more weight than did the horses on a hay-only diet.

Similarly, the only difference they noticed in size of particles in the feces was in relation to diet. The average fecal particle size was significantly larger in in horses fed hay only or hay and oats, compared with the hay and pelleted diet. (Fecal particle size in this study was smaller than in previous studies, possibly due to the mixing technique that was used. However, there were significant differences between the different feed groups, so the researchers felt that their results were valid.)

They did notice a significant increase in water intake in treated horses following routine dental care. There was no obvious explanation for this, as floating did not affect any other variable examined in the study.

Dr Carmalt concludes that routine dental treatment has no significant effect on weight gain or improvement in body condition in normal horses. Neither does it improve the horse's ability to chew and digest its food. On the other hand there was a significant association between the type of food and weight gain. In other words, any increase in weight is due to dietary change rather than the act of floating.

Dr Carmalt points out that this study looked at the healthy pregnant mares. It did not examine the effect of floating on longer-term dental health, nor did it assess whether treating severe abnormalities such as fractured teeth would have an effect. These horses were not being ridden and so the effect of the dental procedures on the response to a bit was not examined.
Written by Mark Andrews.
For more details see: Effect of dental floating on weight gain, body condition score, feed digestibility and fecal particle size in pregnant mares. James L Carmalt, Hugh GG Townsend, Eugene D Janzen, Nadia F Cymbaluk. JAVMA (2004) 225, 1889 - 1893